Soon all Habitat homes will meet Energy Star standards. A Habitat affiliate in Florida is already exceeding Energy Star standards in some of its new homes.

Habitat for Humanity of Lakeland, Florida, began building energy-efficient homes in 2000 and now exceeds Energy Star standards on all its new homes. Lakeland Habitat is one of 1,600 U.S. affiliates of Habitat for Humanity International, a non-profit organization that partners with needy families and volunteers to build simple, decent, affordable housing. Habitat’s U.S. affiliates collectively built over 5,600 homes in 2007, making Habitat the country’s fourteenth largest builder, according to Builder Magazine.

Habitat International is heavily promoting energy efficiency and green construction. In December 2007, Habitat issued guidelines asking all of its affiliates to build homes that meet Energy Star efficiency standards and in 2009 it will begin requiring affiliates wishing to receive grants from the main organization to meet Energy Star criteria.

KEY ENERGY-SAVINGS FEATURES

The Lakeland Habitat for Humanity homes meet or exceed Energy Star standards for new homes. They have the following energy-saving features:

Ducts are in conditioned space using a framed-in duct chase (in many homes).

Air handlers are in an interior closet.

Duct system joints and plenums are sealed with water-based mastic and fiberglass mesh, then tested to ensure duct leakage below 6%.

“I was so exited when I saw Habitat’s new criteria document; this is exactly what Habitat’s home owners need,” says Claire Twomey, executive director of the Lakeland Habitat affiliate and the guiding force behind its move to energy efficient construction. Lakeland Habitat built its 60th home in 2008 and plans to construct more than 17 new homes in 2009, all exceeding Energy Star efficiency standards. Twomey’s goal is to begin pursuing LEED Green Home certification on all its new homes within a year.

Energy Efficient

Lakeland Habitat received technical support from the U.S. Department of Energy (DOE’s) Building America Program and its research partners, energy consultant Ken Fonorow and the Florida Solar Energy Center (FSEC). They helped Lakeland Habitat put together an energy efficiency strategy based on solid building science principles. In 2008, Lakeland Habitat completed its 60th home. All of its homes now exceed Energy Star standards, and some have achieved savings as high as 34% over code-built homes (see “Key Energy-Saving Features”).

One of the key elements in Lakeland Habitat’s energy efficiency strategy is placing the air handler in a closet within the conditioned space, where there is less heat gain and heat loss than there would be in the attic or in a garage. Ideally, the entire heating-and-cooling system would be inside the conditioned space. Lakeland Habitat has built many houses that included duct systems in conditioned space; however, it has reverted to ducts in the attic in some recent homes, because volunteers were more comfortable with this method. The interior air handler closet is the only energy feature that affects the design of the house. The rest of the energy package could be implemented in any home design.

According to Twomey, little changes add up to big savings. “Mostly it’s small things, like caulking around all of the wiring and plumbing, caulking the sill plate, sealing the ducts, and adding a radiant barrier. The radiant barrier is like thick, flexible aluminum foil. You staple it under the roof between the rafters,” Twomey explains. Research has shown that a radiant barrier can reduce heat gain through the ceiling by an average of 20°F, and ceiling heat flux by 25%–50%, with annual cooling electricity savings of 7%–10%. If the ductwork is locatedin the attic, the radiant barrier has the added benefit of reducing heat gain and loss to the ducts, so the air conditioner doesn’t have to work so hard during Lakeland’s long cooling season.

Lakeland Habitat’s homes follow Energy Star’s Thermal Bypass Inspection Checklist, which calls for, among other things, a continuous air barrier to limit infiltration. Lakeland Habitat conducts blower door tests on the homes to measure the airtightness of the envelope. “You have to pay attention to what your subcontractors are doing. They have to know what your goal is, and they have to know what it looks like to do it right,” says Twomey. “Testing is very critical to ensure good results. It’s very rewarding to the volunteers when the house scores high and they know they’ve done it right.”
Lakeland Habitat also tests the ducts for air leakage. “All of our houses meet the 6% duct leakage limit of Energy Star,” says Twomey. Leakage in typical new construction in Florida homes is sometimes as high as 15%.

“We had one house that we had tested and the duct leakage score was terrible. Our air conditioning contractor used two crews—one to install and one to come back to do the sealing. On this house they never came back to do the sealing. We would not have known this if we had not tested the house,” says Twomey.

Energy Upgrades Boost Health, Durability, and Sustainability Too

Many of the energy improvements provide other benefits as well, including improved indoor air quality (IAQ), durability, and comfort. Excellent IAQ in energy-efficient houses results from installing sealed-combustion heating and water heating (when gas is used); sealing the duct system; limiting infiltration; providing filtered outside air ventilation; and installing ducted kitchen and bath exhaust fans to remove moisture generated by cooking and bathing. Careful attention to sealing the continuous air barrier by caulking and filling any cracks and penetrations in the walls, floors, and ceilings improves energy efficiency while keeping out humid outside air, insects, and pollen. Roach dander and pollen are major asthma and allergy triggers. Humid outside air drawn through the wall and ceiling assemblies can deposit moisture in framing cavities, degrading the effectiveness of insulation and promoting rot and mold growth. Properly sealing the ducts reduces the risk of condensation in and around ducts, another source of mold and rot, and helps to maintain neutral air pressure in the house to further limit infiltration.

This attention to air sealing also helps to prevent drafts from room to room, which improves the comfort of the home. Other energy efficiency measures that improve occupant comfort include low-emissivity windows and deep window overhangs, which keep out ultraviolet rays that create glare and fade carpets and furniture; extra insulation, which adds soundproofing; and the radiant barrier, which helps to keep the attic cool.

Dollars and Sense

“People talk about payback periods with energy efficiency measures,” says Twomey. “But our homes essentially have instant payback. If there is a slight increase in cost to cover the cost of energy efficiency improvements, we can just adjust the length of the homeowner’s mortgage, so that they have a home they can afford. And because it’s energy efficient, they can afford to keep it.”

“We figure it costs about $1,500 more per house to build in these energy efficiency features,” says Twomey.

Twomey has seen much higher energy savings than are shown in this table. “We tracked utility bills on our first house for five years and compared them to a house with the same square footage and same family size that was built six months earlier without the energy efficiency changes. Utility savings were 60%. Dollar-wise, that equates to savings of at least $150 per month.”

Twomey notes that, depending on what they are moving from, some homeowners will see even bigger energy bill savings. “Some of our homeowners are coming from old rental homes where they were paying $400 or $500 per month in utility bills. There is very little utility bill assistance here, so if you can’t pay your bill, the utility company will shut off your electricity. It’s almost criminal to build houses for people who can afford the mortgage but cannot afford the utility bills.”

Twomey also notes that local rebates can make energy-efficient construction much more affordable for the builder and the home owner. “Our county gives us up to $5,000 for every home built to their energy efficiency requirements. Using 14-SEER A/C is one of the county’s requirements. Going from 13- to 14-SEER costs $500 more, but it’s worth it to earn the $5,000.”

Fonorow echoes the thoughts of many energy-conscious Habitat affiliates when he says, “We need to think of affordability not just in terms of how much it costs to buy the home but also in terms of how much it costs the family to run the home once they’re in it.” Fonorow notes that the Bureau of the Census did a study a few years ago and concluded that the average low-income person spends 18% of his or her income on the utility bill. “If you made $50,000 a year,” he says, translating this percentage into a middle-income salary, “that would equal $800 a month for utilities.”
Janet McIlvaine, Building America liaison to Habitat, recommends that affiliates work with a HERS rater to determine a package of energy savings that will result in a positive cash flow during the first year of occupancy. Many RESNET certified raters have expressed interest in volunteering with Habitat through a national RESNET community service project (see “Raters Offer Time and Talent to Habitat for Humanity,” HE Jan/Feb ’09, p. 8).

The Bottom Line

“We are morally obligated to help our future generations to conserve energy,” says Twomey. “It doesn’t matter whether you’re low income or very wealthy; everyone should have access to energy-efficient homes. It takes a little extra time and effort, but it’s worth it.”

Theresa Gilbride is a scientist at Pacific Northwest National Laboratory, Richland, Washington, which supports the Building America program for the U.S. Department of Energy.

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The Residential Energy Services Network (RESNET), Building America, and Habitat for Humanity have partnered to recruit certified home energy raters willing to volunteer rating services to a Habitat affiliate in their area. When a rater ...